The invention relates to protective breathing equipment comprising a breathing mask, a harness enabling it to be put quickly into place on the face, and sometimes also goggles for providing protection against smoke, and optionally integrated with the mask.
Protective breathing equipment that can be donned quickly is already known (EP-A-0 288 391), in particular for the technical crew of passenger carrying airplanes, the equipment comprising a breathing mask provided with a regulator for connection to a source of pressurized breathing gas (generally oxygen) and a harness having at least one extensible strap whose ends are connected to the mask and which includes an element that is temporarily inflatable by the pressurized gas to lengthen the strap until it is large enough to enable the user to engage the harness on the head, and can be scavenged to cause the strap to tighten so as to press the mask against the face and hold it in place.
The equipment described by way of example in document EP 0 288 391 enables the pressure in the inflatable element to be adjusted so as to give it a value between the complete deflation pressure and the fully inflated pressure so as to reduce the discomfort created by wearing the mask continuously under conditions of flight that make it compulsary to wear the mask.
That solution is entirely satisfactory from the comfort point of view. However, it complicates the pressure control means. Furthermore, inevitable leaks, e.g. due to the porosity of the inflatable element, lead to breathing gas under pressure being consumed during periods while the mask is being used in the xe2x80x9ccomfortxe2x80x9d position.
The present invention seeks in particular to provide protective breathing equipment that provides a degree of comfort at least equivalent to that of existing equipment during periods in which the mask is worn while there is no need to press it hard against the face to overcome the high pressure of the breathing gas, and that reduces breathing gas consumption during these periods.
For this purpose, the invention provides in particular equipment of the above-defined kind, in which the extensible strap is connected to the face-piece via at least one mechanical member of length that is adjustable by the user while wearing the equipment.
The mechanical member may be constituted by a rack fixed to one end of the strap and a pawl carried by the face-piece, allowing the strap and the face-piece to move relative to each other in the tightening direction, the pawl being releasable to allow the rack to move in the opposite direction. This disposition can be inverted, with the rack then being fixed to the face-piece.
The pneumatic connection between the face-piece, which carries the means controllable by the user for inflating the inflatable element, and said inflatable element is designed to allow for relative sliding. In order to ensure that the inflation command causes the rack to come into its position of maximum tightness, this result can be achieved by extending the rack by a hollow piston that is movable in a cylinder fast with the face-piece. The piston then divides the cylinder into two compartments, one of which is connected to the inflation feed for the inflatable element and the other of which is connected to the atmosphere.
The protection equipment can be associated with an aneroid capsule constituting an altitude detector for automatically causing the cylinder compartment to be put at the pressure which gives rise to maximum tightening in the event of depressurization of the environment.
The above features and others will appear more clearly on reading the following description of particular embodiments given as non-limiting examples.